Overview
EN ISO 19957:2021 (ISO 19957:2021) specifies a standardized test method to measure the force required to pull a single heel pin out of a heel. The procedure quantifies heel pin holding strength of heel materials (using a standard pin and controlled insertion) and is used to assess heel nailing in commercial production. This European adoption by CEN supersedes the 2004 edition and applies primarily to plastic and wooden heels for women’s footwear. Heels made from layered fibreboard or leather, and low plastic men's heels, are excluded.
Key topics and technical requirements
- Test principle: Measure the force to extract a single heel pin; express results as heel pin holding strength = pull-out force divided by effective buttressing length (N/mm).
- Apparatus:
- Tensile testing machine complying with ISO 7500-1, class 2, range ≈ 0–2 000 N; traverse rate 40 mm/min ±10 mm/min.
- Small clamp/slotted hook, commercial heel nailing machine, and a 2 mm metal rod for fixturing.
- Standard heel pin (Figure 1): length 18 ± 0.5 mm; diameter over buttress ridges ≥ 1.9 mm; ≥ 13 buttress flanks; distance from point to first buttress base ≥ 12 mm.
- Sampling & preparation:
- Typical sampling: three heels with six pins each (or four heels with four pins each if six not possible).
- For material property tests: use three 2 mm cellulose fibreboard discs (~45 mm) stacked and positioned during pin insertion to control penetration.
- Required pin penetration after disc removal: uninserted pin length (including head) between 5 mm and 8 mm (reject and rework if outside limits).
- Attachment to the tensile machine: drill a horizontal 2 mm hole through the heel (typical position 20–25 mm from top; 15–20 mm for heavily undercut designs) or clamp narrow stems directly.
- Reporting: include test conditions, specimen preparation, pin dimensions, measured forces, calculated N/mm strength, and any deviations.
Applications and users
- Quality control and production inspection for footwear manufacturers (especially women’s high and varied heels).
- R&D and materials evaluation for heel designers and material suppliers to compare heel materials’ resistance to pin pull-out.
- Accredited testing laboratories performing conformity checks and durability assessments.
- Technical compliance and procurement teams specifying heel nailing performance for contracts or standards compliance.
Related standards
- ISO 7500-1 - calibration and verification of static uniaxial testing machines (referenced for tensile machine requirements).
- Adopted in Europe as EN ISO 19957:2021 (CEN endorsement).
Keywords: ISO 19957, EN ISO 19957:2021, heel pin holding strength, footwear testing, heel testing, tensile testing machine, heel nailing, heel materials, quality control.
